1. Field of the Invention
The present invention relates to a fuel cell including a membrane electrode assembly and separators sandwiching the membrane electrode assembly. The membrane electrode assembly includes a pair of electrodes and an electrolyte membrane interposed between the electrodes. A first reactant gas flow field is formed in the fuel cell for supplying one reactant gas along one electrode surface of the membrane electrode assembly, and a second reactant gas flow field is formed in the fuel cell for supplying the other reactant gas to the other electrode surface of the membrane electrode assembly.
2. Description of the Related Art
For example, a solid polymer electrolyte fuel cell employs a membrane electrode assembly (MEA) which includes an anode, a cathode, and an electrolyte membrane interposed between the anode and the cathode. The electrolyte membrane is a polymer ion exchange membrane. The membrane electrode assembly is sandwiched between separators to form a power generation cell (unit cell). Generally, several tens to hundreds of unit cells are stacked together to from a fuel cell stack for use in a vehicle.
In most cases, in order to supply a fuel gas and an oxygen-containing gas as reactant gases to the anode and the cathode of each of the stacked power generation cells, the fuel cell has so called internal manifold structure. The internal manifold includes reactant gas supply passages and reactant gas discharge passages extending through the power generation cells in the stacking direction. The reactant gas supply passages and the reactant gas discharge passages are connected to inlets and outlets of reactant gas flow fields for supplying reactant gases along electrode surfaces.
In this case, the opening areas of the reactant gas supply passages and the recant gas discharge passages are relatively small. Therefore, in order to enable such reactant gases to flow in the reactant gas flow fields smoothly, buffers for dispersing the reactant gases are required to be provided adjacent to the reactant gas supply passages and the reactant gas discharge passages.
For example, in a fuel cell disclosed in Japanese Laid-Open Patent Publication No. 11-283637 (hereinafter referred to as conventional technique 1), as shown in FIG. 18, a plate body 1 is provided. On both sides of both ends of the body 1, a first through hole 2a, a second through hole 3a, a third through hole 4a as supply passages of a hydrogen gas, an oxygen gas, and coolant water, and first through hole 2b, a second through hole 3b, and a third through hole 4b as discharge passages of the hydrogen gas, the oxygen gas, and, and the coolant water are formed.
A hydrogen gas flow field 5 is formed at a central portion of the body 1. The hydrogen gas flow field 5 is connected to the first through hole 2a and the first through hole 2b for allowing the hydrogen gas to flow from the first through hole 2a to the hydrogen gas flow field 5, and flow from the hydrogen gas flow field 5 to the first through hole 2b. A fin-like guides 6 for guiding the hydrogen gas from the first through hole 2a to the hydrogen gas flow field 5, and a fin-like guides 7 for guiding the hydrogen gas from the hydrogen gas flow field 5 to the first through hole 2b are provided in portions of the body 1 which are in contact with the hydrogen gas.